The use of aluminum in heat exchangers is now widespread in applications such as automotive, off road equipment and heating ventilation and air conditioning (HVAC) systems. Extruded tubing is often used due to the ability to produce complex thin wall geometries such as mini microport (MMP) tubing which improves heat transfer. Such tubes are typically connected to fins and headers/manifolds to create the heat exchanger using controlled atmosphere brazing (CAB). Resistance to failure by pitting corrosion is an important property of these units which can be subjected to corrosive environments such as road salt, coastal environments and industrial pollutants. At the same time, the expectations in terms of lifetimes of the units and customer warranties are increasing and there is a continuing need to improve the corrosion performance of such systems. The extruded tubing is typically the thinnest walled component of such heat exchangers and the most likely to fail by corrosion first. Often the tubes are zincated either by thermal arc spray or by roll coating with a zinc containing flux which adds a measure of sacrificial corrosion protection. However, the inherent corrosion resistance of the underlying tube material remains a key component of the protection mechanism, particularly when the sacrificial Zn rich layer has been removed by corrosion.
The present composition and method are provided to address the problems discussed above and other problems, and to provide advantages and aspects not provided by prior compositions and methods of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.